Abstract
ABSTRACT Guava is a fruit that stands out for its aroma, intense flavor, vitamins, and minerals. Its availability as a powdered food enhances its commercial applications. This study aimed to evaluate mathematical models for adsorption isotherms and determine the properties and flowability of guava pulp powder obtained by foam-mat drying. The models of GAB, BET, Henderson and Oswin were fitted to determine the isotherms of powders with 4 and 8% albumin, at temperatures of 35°C and 45°C. The powders were evaluated by wall friction angle, flow index, apparent density, and particle microstructure analysis. The best fit to the isotherms was obtained by the GAB model. Wall friction angle ranged from 15.7 to 21.9° and from 13.6 to 20.4° for samples containing 4 and 8% albumin, respectively. Higher densities were observed in the powder containing 8% albumin. The powders were classified as easy flowing when the flow index was between 8.00 and 8.68. The presence of albumin in powders resulted in particles with less rough surfaces, less hygroscopicity, and improved flowability.
Highlights
Guava (Psidium guajava L.) is an easy-to-grow tropical fruit tree in Brazilian territory and stands out due to high vitamin C content in its fruit
The GAB and Henderson models had the best to the experimental data, but the GAB model had the smallest averages. Both models had less than 10% errors for all temperatures and albumin concentrations
The isotherms of guava pulp powders were wellfitted by the GAB model and classified as type III
Summary
Guava (Psidium guajava L.) is an easy-to-grow tropical fruit tree in Brazilian territory and stands out due to high vitamin C content in its fruit. It has high amounts of sugar, vitamin A, vitamin B, phosphorus, iron, and calcium (Silva et al, 2014). Like most fruits, are highly perishable and require processing to increase shelf life, transforming them into new products (Infante et al, 2013). Drying methods enable processing of fruit into a powder, increasing product shelf-life and added value, allowing its use in a wide range of food formulations on an industrial scale (Mata et al, 2005). Adsorption of water by dehydrated foods is mainly caused by the chemical nature of its organic components, such as the presence of sugars, Van der Waals intermolecular forces, bonds between OHhydroxyl groups and water molecules, and dehydration process type (Park et al, 2008)
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